Control for varying the cross-sectional area of a nozzle



July 3, 1932 J. H. BERTIN ETAL 3,041,823

CNTROL FOR VARYING THE CROSS-SECTIONAL AREA `OF' A NOZZLE Filed sept. 14, 1955 INVENToRs invii/Veys United States Patent Oiilice 3,ii4l,823 Patented July 3, 1962 3,641,323 CNTRUL FR VARiZiNG 'IHRE CRSS-SEQTIONAL AREA F A NZZLE Jean H. Bertin, Neuiily-sur-Seine, Louis A. J. Ranger, Vanves, and Marcel iadosch and Francois lVi. L. Maunoury, Paris, France, assignors to Societe Nationale dEtude et de Construction de Moteurs dAviation, Paris, France, a company oi France Filed Sept. i4, 1953, Ser. No. 379,896 iaims priority, application France Sept. 13, 1952 2 Claims. (Ci. nti-35.6)

In the U.S. patent application, Ser. No. 263,666, tiled December 27, 1951 is described a method of control of the cross-sectional area of a discharge nozzle and, in particular of the cross-sectional area of a discharge nozzle of a reaction propulsion unit, according to which method there is directed on to the flow to be controlled, an auxilliary jet of gas, the pressure of which is higher than that of the main flow and the speed of injection of which has a component perpendicular to this latter. This auxiliary jet may be produced by a blowing slot which extends around the whole periphery of the discharge nozzle and, in the case of the discharge nozzle of a reaction unit, in the neighbourhood of its outlet orifice. There is thus created a kind of throttlingr action of the jet to be controlled, by means of a jet of annular form.

The output of the auxiliary jet which serves to bring about this fluid constriction may be a small fraction (and that fraction may be varied) of the output of the main ow and may for example be derived from the combustion chambers of the reaction unit or from a less hot source such as the air compressor; in the latter case, it is desirable to heat the air in o-rder to increase the amount of its movement.

The present invention is concerned with an improvement in the devices for putting into eifeet this method of control of the cross-sectional area of a discharge nozzle, and in accordance with this improvement the auxiliary uid which is to be used lto produce the constrictive jet is led to the blowing slot arrangement through a passage of generally annular shape which surrounds the discharge nozzle; the internal wall of this passage may be constituted by the wall of the discharge nozzle itself.

In accordance with one form of embodiment of the invention when applied to discharge nozzles of reaction units, the annular passage terminates in an annular convergent nozzle co-axial with the outlet orifice of the discharge nozzle of the reactor, means being provided tor closing either the said annular nozzle or the blowing slot.

This form of embodiment tinds one of its most important applications in the control of the cross-sectional area of the outlet of a discharge nozzle of a reactor provided with a post-combustion device arranged inside the said exhaust nozzle. It is known, in fact, that the cross-section of such a discharge nozzle must be varied in dependence on whether the post-combustion device is in operation or is not in operation, the said cross-section being reduced in the latter case by shutting oft the annular nozzle, the blowing slot being then open; on the other hand, when it is desired to obtain an increase in thrust, the post-combustion device is put into operation and the blowing slot is shut oi, which causes the opening of the annular nozzle and the expansion of the auxiliary gas under pressure takes place co-axially through this annular nozzle with respect to the main reaction jet. ln this way, a practically constant output is obtained in the annular passage whatever the position of the shutting oli devices may be.

The description which follows below with respect to the attached drawings (which `are given by way of example only and not in any sense by way of limitation) will make it quite clear how the invention may be put into 2 eect, the special features which are referred to, either in the drawings or in the text, forming, of course, a part of the said invention.

FIG. l is a diagrammatic View in axial cross-section of a turbo-jet unit in which the jet is reheated by post-combustion, and which is provided with the improvement in accordance with the invention.

FIGS. 2, 3a and 3b are respectively diagrammatic crosssections at the points II-II, Illa-Illa .and IIIb--Ilib of Fig. 1.

The turbo-jet unit shown in the drawing comprises a frontal `air inlet opening 1, an air compressor 2, combustion chambers 3, a gas turbine 4 operated by the discharge from these chambers and ,driving the compressor 2, and lastly, the exhaust nozzle 5 directed towards the rear and supplying the propulsive reaction jet. The exhaust nozzle 5 includes a zone 5a of greater width in which are arranged post-combustion burners 6 which are put into operation when it is desired momentarily to develop an increase in thrust. These burners 6 are mounted on radial arms 7. The fuel, supplied at `a suitable rate, is conveyed under pressure by the fuel pump 8 to the inject-ors 9 through the piping system 1t) and the injection distributor 11.

The hot flow of air and burnt gases which is discharged at high speed from the turbine is slowed down in the divergent portion 5a of the discharge nozzle, until it attains a suitable speed which permits of a good mixture of the gases with the vaporised fuel delivered by the injectors 9. The ignition of the mixture is obtained by means of a sparkplug 12 supplied from a special electric circuit (not shown). The combustion takes place in the cylindrical portion 5b of the discharge nozzle and the expansion in e latter portion of the nozzle 5.

As the cross-section of the outlet of a well designed discharge nozzle should be very nearly proportional to the square root of the temperature of the gases discharged, it will be seen that in a reaction unit of the type described, the cross-section of the outlet orice of the discharge nozzle should vary to a fairly considerable extent, depending on whether. the burners 6 are or are not .in operation. In the form of embodiment shown, the material cross-section of the outlet oriiice is chosen in such a way as to be large enough for the discharge of Ithe gases when they are heated by the burners 6, the latter being operative. As this cross-section is thus too large when the burners are not in operation, that is to say at starting up and at cruising speed, this cross-section is reduced -by producing a iiuid constriction elect by means of a gas under pressure which is introduced through a peripheral blowing slot 13 located close to the outlet orifice, as has been described in the patent application referred to above.

In accordance with one form of embodiment of the present invention, this blowing slot communicates with 'an annular chamber 14 formed on the one side lby the casing 15 of the reaction unit and, on the other a second casing 16 co-axial with the tir-st. The annular chamber 14 communicates in addition ywith the combustion chamber 3 through orices 17 which are formed in the wall 15 of these chambers. The annular chamber discharges to atmosphere through a convergent annular nozzle 18 concentric with the outlet orifice of the exhaust `discharge nozzle 5.

In this way, the annular chamber '14 constitutes, at the same time a collector for the gases under pressure taken from the combustion chambers 3, and a passage through which the gases may be led to the blowing slot 13 and to the convergent nozzle 18. A series of imbricated shutters such as 19, arranged in a ring between the casing =15 and the casing 16 co-operating with each other and actuated by a jack 20, are adapted to close either the blowing slot 13 or the annular discharge nozzle 18. The

side by @penses shutters may be arranged in the same way as the cooling control shutters in the cowlings of piston-type aircraft engines, as shown in FIGS. 3a and 3b.

The arrangement is constituted in such a manner that, when the nozzle 18 is closed, the blowing slot 13 is open and vice-versa. In this way, the gas under pressure may be discharged either through the slot 13 or through the annular nozzle 18. FIG. l shows the shutters in position in the upper portion of the exhaust nozzle, the blowing slot being open, and in the lower portion the position of the shutters is such that the blowing slot is closed and the annular nozzle is open.

The two extreme positions of the shutters are obviously not the only ones which are possible: infact, the shutters operated by the jack 2li could remain in any intermediate position between the two preceding ,.positions, in such a way as to ensure the control of the ouput of gas passing through the slot 13 to the value necessary for obtaining the desired cross-sectional area of the exhaust discharge nozzle.

In order to facilitate the assembly of the shutters and to reduce their number, the blowing slot may be broken up and constituted by segmental portions. The eflicacy of such a slot is almost exactly the same as that of: a continuous slot having the same cross-sectional area of passage.

It is quite clear that .the device for shutting oli the blowing slot and the annular nozzle by means of a series of shutters controlled by a jack only represents one example of embodiment of the control of the constriction of the jet and that all arrangements having this same object fall within the scope of the invention.

In addition, as has already been indicated in the above mentioned patent application, instead of deriving the auxiliary gas intended to form the constrictive jet from the combustion chambers 3, it may be derived from the output side of the air compressor, and preferably from a high pressure stage.

During the operation of the turbo-jet unit without reheating, the auxiliary gas obtained from the compressor or from the combustion chambers is led under pressure to the intake of the slot 13 in which it expands. In this way, the outlet cross-section of the discharge nozzle 5 is controlled in accordance with the conditions of use of the engine, that is to say in order to obtain the desired conditions:

The exhaust nozzle closed at maximum speed without reheating,

The discharge nozzle cruising speeds.

At the precise moment at `which the re-heating of the jet is put into operation, that is to say when the fuel is injected into the exhaust nozzle by the burners 6, the supply of gas to the blowing slot is cut oit and the geometric cross-section at the neck of the nozzle 5 increases for this reason. The post-combustion works correctly by keeping the turbo-jet unit Within the normal operating conditions. The gas under pressure is expanded and discharged to the exterior of -the turbo-jet unit through the annular slot 18 and thus contributes to the thrust of the machine.

In order to return to normal conditions of working, the supply of fuel to the post-combustion burners 6 is cut oi and the blowing gas is simultaneously discharged through the slot 13, thereby controlling the output to the value necessary for obtaining the desired conditions. The air derived from the compressor or the burnt gases derived from the combustion chambers is in contact with the hot walls of the stator of the turbine and of the exhaust nozzle during their passage towards the blowing slot 13, their thermal energy increases and their speed of expansion is thereby increased.

It is known that the etect of constriction obtained by an auxiliary jet depends upon the amount of movement of this jet, that ,is to say on the product of its output-mass closed to a lesser degree for multiplied by its speed of injection. In particular, in

Vorder to obtain a given constrictive eiect, the necessary output of auxiliary gas will decrease as the temperature of this gas rises under pressure.

It is, of course, understood that to the heating of the auxiliary gas by simple thermal exchange with the hot wall l5, there may be added heating devices such as combustion chambers located inside the annular conduit 14 itself, with the object of `further increasing the discharge speed of this auxiliary gas.

The amount of movement of the auxiliary gas may also be increased by increasing its output-mass, for example by injecting into the gas a liquid such as water. This liquid may be very iinely vaporised or added in the form of steam into the body of the auxiliary gas by utilising the heat of the latter. This heat is already sufficient if the auxiliary gas into which the water is injected, is obtained from the air delivered by the compressor. In addition, a liquid having a very low boiling point such as methanol may be chosen for this purpose. f

The injection of liquid may also be combined with heating.

The heating of the blowing gas has as its quite obvious corollary the cooling of the wall 15 of the lexhaust discharge nozzle 5. This advantage is of particularimportance when the high conditions Iof temperature at which the sheet steel members of the discharge nozzle work during the heating of the jet are taken into account. In this way, the thermal energy which is normally exchanged by the yreactor with the external exterior air and lost by the machine is, in this case, recovered and used for propulsion since during the heating period, as indicated above, the gas under pressure is expanded in a nozzle 1S concentric with respect to the main discharge nozzle `5 and discharged to the exterior parallel to the axis of the main jet.

It should be noted that the output of the auxiliary gas always remains at very nearly the same value, whether the reactor operates with or without heating of the jet. In fact, the annular nozzle 18 is dimensioned in such a way that its outlet cross-section is very nearly equal to that of the blowing slot 13. The result of this is that for given operating conditions of the turbo-jet unit and in the case in which the auxiliary gas is taken from the compressor, the point of operation of the latter is always located in the same way on the diagram. The adaptation of the machine is thus quite well detined and the constrictive eiect of the jet does not cause, by reason of the intake of auxiliary air, variations of the points of equilibrium. The number of holes 34.7 will clearly be a `function of the output of the air which is taken and their total effective cross-sectional area must be greater than that of the blowing slot 13 or ofthe nozzle 1S, so that the output of the air is not thereby limited. The actual shape of the holes will be such as to reduce the losses of pressure to a minimum.

It will be quite clear that modications may be made to the improvements which have just been described, and in particular by the substitution of equivalent technical means, without .thereby departing from the spirit or the scope of the pre-sent invention. More especially it is very clear that the present invention may be applied to any reaction propulsion unit which is surrounded over at least a part of its length by a conduit of generally annular form and which is intended to convey a gas under i pressure towards one or more expansion orifices.

Futhermorc, although the use of the casing of the reactor as the internal wall of the annular conduit may be particularly advantageous, since it facilitates the thermal exhanges and reduces the weight of the engine, it is to be understood that the invention will cover the case of a conduit which is spaced away from the casing of the reactor and is contained within two casings separate from that of the reactor. The invention is also to be applied to any embodiment in which the conduit for the auxiliary gas does not completely surround the reactor and which might have a cross-section in the shape of a crescent.

What We claim is:

1. `In a jet propulsion unit having a main variablearea propelling nozzle with an outlet facing rearwardly of said unit, the combination of an aerodynarncally operating auxiliary nozzle for varying the area of said main propelling nozzle in the vicinity of said outlet and opening towards the interior of said main propelling nozzle, to form, when -supplied with pressure fluid, a substantially annular transverse screen-like jet restricting the outlet area of said main propelling nozzle, and of a secondary propelling nozzle adjacent said main propelling nozzle and also facing rearwardly of said unit, to form, when supplied with pressure luid, a rearwardly issuing secondary thrust-producing jet to assist propulsion, valve means being provided for inversely varying the supplies of pressure fluid to said auxiliary nozzle and to said secondary nozzle.

2. Unit as claimed in claim 1 wherein the valve means is designed `for completely obturating, in one extreme position thereof, the auxiliary nozzle to allow full supply of pressure uid to the secondary nozzle, and, in another extreme position thereof, for completely obturating the secondary nozzle to allow lfull supply of pressure tluid to the auxiliary nozzle.

References Cited in the le of this patent UNITED STATES PATENTS 2,458,600 Imbert et al Jan. 11, 1949 2,487,588 Price Nov. 8, 1949 2,587,649 Pope Mar. 4, 1952 2,597,253 Melchior May 20, 1952 2,603,060 Brown July 15, 1952 2,603,062 Weiler et al. July 15, 1952 2,630,673 Woll Mar. 10, 1953 2,639,578 Pouchot May 26, 1953 2,651,172 Kennedy Sept. 8, 1953 2,692,800 Nichols et al. Oct. 26, 1954 2,703,959 Wetherbee Mar. 15, 1955 2,753,685 Mattinson July 10, 1956 2,763,984 Kadosch et al. Sept, 25, 1956 OTHER REFERENCES Anti-Bomber Rocket Missiles by Chandler Aero Digest April, 1950l pp. 10D-102. 

